Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Patent
1997-02-27
2000-10-31
Michl, Paul R.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C08K 504
Patent
active
061404012
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to the use of a stabilizer combination for molding compounds based on polyvinyl chloride (PVC) in the production of semirigid and flexible films of polyvinyl chloride by the calendering process for avoiding plate-out on the rolls used. In the context of the invention, the expression "molding compounds based on polyvinyl chloride" is understood to include both molding compounds based on conventional homopolymers or copolymers of vinyl chloride and those based on blends of polyvinyl chloride compounds with other polymers. The expression also encompasses suspension, bulk and emulsion polyvinyl chloride.
BACKGROUND OF THE INVENTION
Hitherto, liquid barium/cadmium stabilizers have normally been used in the thermoplastic processing of semirigid PVC and flexible PVC to form films by the calendering process. However, since toxic heavy metals, such as cadmium, are no longer acceptable today for reasons of factory hygiene and ecology, stabilizer systems based on liquid barium/zinc stabilizers have been increasingly used for the application mentioned. However, since the heavy metal, barium, also shows relatively high toxicity, there is a general trend in practice to replace these barium/zinc stabilizers also by physiologically safe calcium/zinc stabilizers.
In the calendering of flexible and semirigid PVC, the stabilizer system used has to meet stringent requirements. On the one hand, good early colors coupled with adequate color hold are required; on the other hand, the calendering process and the film properties often additionally required, such as good weathering resistance, not only have to guarantee excellent long-term stabilities, they are also expected to ensure problem-free regenerate processing. In addition, the stabilizer systems used should also reduce the tendency towards blocking and, hence, should enable the film to be removed more easily from the hot calender rolls and should have such rheological properties that the films are free from flow structures and do not have any defects. All these requirements have to be viewed in particular against the background of the high calendering speeds now typically encountered in practice. Another crucial requirement which stabilizers used for this purpose are expected to satisfy is the following: they should not cause any plate-out on calender rolls, take-off and cooling rolls or on any following embossing and laminating units.
The liquid Ba/Cd and Ba/Zn stabilizers normally used for the production of semirigid and flexible PVC films adequately satisfy the requirements discussed above. Although Ca/Zn stabilizers do not cause any plate-out on calender rolls, they often show only inadequate thermal stability and long-term stability. By contrast, hitherto known solid Ca/Zn stabilizers show the required long-term stability coupled with good early colors and color hold providing relatively large quantities of metal soaps are used. Unfortunately, stabilizers such as these cause such serious plate-out on calender rolls that they cannot be used in practice for the production of calendered films of flexible or semirigid PVC.
On the subject of known stabilizer systems containing calcium and/or zinc salts of fatty acids, reference is made for example to the following publications:
DE-A-31 13 442 relates to stabilized PVC molding compounds containing a stabilizer combination based on alkali metal, alkaline earth metal and/or zinc soaps, co-stabilizers, fine-particle crystalline water-containing alkali metal alumosilicates, lubricants and, optionally, other typical additives. Crucially, these stabilizer combinations--in addition to an alkali metal alumosilicate--must also contain a co-stabilizer selected from .beta.-diketones, .alpha.-ketoenol esters, .alpha.-acyl lactones, substituted 1,4-dihydropyridine dicarboxylic acids and optionally substituted pyrroles. In one preferred embodiment, calcium soaps are used in conjunction with zinc soaps.
EP-A-0 027 588 describes stabilizer combinations for PVC molding compounds which contai
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Brand Ernst-Udo
Klamann Joerg-Dieter
Peters Arthur
Wedl Peter
Drach John E.
Ettelman Aaron R.
Henkel Kommanditgesellschaft auf Aktien
Meder Martin G.
Michl Paul R.
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